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How do I hard chrome plate 6m long jobs in my vertical tanks systems

Dear Sir,

I am an upcoming entrepreneur based in India. My name is Dhawal. Please suggest how do I hard chrome plated 6 meter long jobs of 40 mm diameter and 100 mm diameter. Presently I am giving current from the top. The problem is the current is not reaching the bottom thereby leading to lesser plating in lower portion of the bar.

Please help. This is very crucial.

Regards
Dhawal

Dhawal Suri
Plating shop owner finding things difficult - Pune, Maharashtra, India
August 18, 2009

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First of two simultaneous responses -- August 22, 2009

You need excellent jigging that goes to the bottom and to the top of the part. Aluminum will work, but plastisol covered copper might be a better choice. Cross section for copper is 1 square inch per 1,000 amps of current. If you go the copper route, you need to inspect the plastisol at least daily so that it does not contaminate the chrome solution if there is a tear.
I assume that you know that chrome requires a very solid contact(s) to work well.
Are you going to use tank anodes or conforming anodes?
Remember to keep your anodes active or you will not plate.
Are you aware that anodes in chrome drop off in how well they work after a given number of hours? I melted down and replaced conforming anodes about once a month to avoid the problem.
Be aware that the anode should not go as deep as the part goes so you do not get really excessive plate on the bottom.
How are you going to keep a tank this deep at the same temp, from the bottom to the top?

James Watts
- Navarre, Florida

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Second of two simultaneous responses --

Apply the current to both ends of the workpiece

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
August 23, 2009

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August 27, 2009

Hello.

I am Saumil. I am from India. We have just bought a factory to start manufacturing of C45 hard chrome plated piston rods of diameter 25mm to 150mm. The lengths of the bars will vary from 3 to 4 metres.

In the earlier plant (which was meant for big jobs), we used to hard chrome plate two piston rods at a time in a square tank of 1 metre by 1 metre using tin-lead alloy anode of diameter 300mm thereby leading to high power bills due to huge heating requirement.

Looking at our production demand, we are planning to hard chrome plate atleast 4 hard chrome plated bars at a time.

Now my questions
1) What should be the length and breath of vertical hard chrome plating tanks so as to enable production of 4 piston rods at a time? What I mean is whether a square arrangement of 2x2 is preferable or all 4 pistons in a row thereby making the tank a narrow one. In either case please mention the approximate length and breadth.

2) What should be the distance between the anodes and the job? I am asking this as I have heard from people that the bath solution changes from trivalent to hexavalent if one places the anode too close to the job.

3) Also, will I need a cooling system to maintain the temperature? I am asking this as the tanks are going to be smaller and the anode is going to be closer to the job. This need is not felt in my first plant as tanks are huge.

4) Also, should I polish or buff the piston bars post plating i.e. which process is better buffing or belt-polishing for better lustre post plating.

Thanks.

Eagerly awaiting comments.

Saumil Mehta
Just started a plating shop - Mumbai, Maharashtra, India

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using confirming anode would be the best possible way to handle this job.
and as for applying current from both ends, Al. section will be least risky tanh copper bus bar, and for maintaining even temperature I would suggest using oil free air agitation

Mahendra
ELECTROPLATERS - BELGAUM, KARNATAKA, INDIA
August 28, 2009

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August 31, 2009

If I were using conforming anodes, I would go with the square as it is easier to work with unless you have nearly unlimited linear distance to work with. This also allows you to load the anode with the part. If you are using tank anodes, with the length of the part, you will find it a bit difficult to load the part and not touch the anode. You can make a loading jig, but it is one more step.
I also think that tank anodes are going to give you uneven plating around the dia.
If you are not plating landing gear, I would try to make a trip to a shop that does landing gear as they tend to be long and heavy and require precise plating.

James Watts
- Navarre, Florida